Liberian health officials said a second case of Ebola has been confirmed.
The news comes months after the West African country was declared Ebola-free.
Officials said a 5-year-old boy tested positive and has been brought to a treatment center in the capital city of Monrovia.
The boy apparently contracted the virus from his 30-year-old mother, who died Thursday.
Liberia is investigating how the woman got to Monrovia with three of her children. Health officials said the woman appears to have come from Guinea, with no symptoms of Ebola, when the country's border was closed.
More than 11,300 people have died from Ebola. Most of the deaths have been reported in Sierra Leone, Liberia and Guinea, since the December 2013 outbreak.